Article

Effects of the spread of the alga Caulerpa racemosa var. cylindracea on the sponge assemblage from coralligenous concretions of the Apulian coast (Ionian Sea, Italy)

Dipartimento di Zoologia, Università degli Studi di Bari, Bari, Italy
Marine Ecology (Impact Factor: 1.08). 08/2009; 30(3):337 - 345. DOI: 10.1111/j.1439-0485.2009.00282.x

ABSTRACT

The present work investigated the modifications induced by the spread of the green macroalga Caulerpa racemosa var. cylindracea (Bryopsidales, Chlorophyta) on the sponge assemblage of Apulian coralligenous concretions (Ionian Sea – Torre Ovo, Italy). The study of qualitative and quantitative sponge composition was carried out before (2004) and after (2006) the spread of this invasive alga by means of traditional (quadrat scraping) and photographic sampling methods. Results indicate that the spread of the green alga is concomitant with a significant decrease in percentage sponge cover both on horizontal- and on vertical-oriented substrates. In addition, strong modifications to the structure of the community in terms of repartition of the available substrate have been observed since the algal spread. Conversely, no major changes have affected the specific composition of the sponge assemblage, suggesting that at this stage of colonization the algal spread has not produced a loss of sponge biodiversity. However, there is a clear need to monitor closely the C. racemosa invasion to verify its long-term impact on the sponge assemblage.

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    • "A survey was performed at each station using a noninvasive method consisting of taking 30 photographic quadrates (50 cm × 50 cm) along a 40-m long horizontal transect, as described in Deter et al. (2012b). Photographic methods are commonly used for the analysis of coralligenous assemblages because they are nondestructive , save time underwater, are repeatable, and enable data archiving (Ferdeghini et al., 2000; Virgilio et al., 2006; Baldacconi and Corriero, 2009; Kipson et al., 2011; Deter et al., 2012a,b). All photographs at a given station were taken from the same orientation and depth, using a compass and a depth meter attached to the quadrate. "
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